In batteries mounted in electric automobiles and hybrid vehicles, many battery cells are connected in series or in parallel in order to increase the output. The lifetime of this type of battery may decrease if it is used in a high temperature environment, and in the case of a battery in which lithium ion cells or the like are connected together, the battery may ignite due to reaching a high temperature during charging. In view of this, in order to avoid such situations, a temperature sensor for detecting the temperature of a power storage element is attached to the battery (e.g., see Patent Document 1).